Mercury inertia switch



March 2, 1937. J R. ERICH MERCURI INEHVTIA SWITCH Filed April 18, 1954INV ENTOR 1 TL 077/ ATTORNEY Patented Mar. 2, 1937 IVIERCUR INERTIASWITCH Reuben Erich, Avenal, Calif., assignor of onethird to William J.Erich and one-third to Walter G. Erich Application April 18, 1934,Serial No. 721,146

1 Claim.

This invention relates to inertia switches, and particularly to oneespecially designed foruse on a motor vehicle, to give direction signalsby reason of changes of speed of the vehicle, and repre- 5 sentsimprovements in construction over the i switch shown in my copendingapplication for patent, Serial No. 668,529, filed April 29, 1933.

The switch as previously constructed was open to the objection that itwas too easily affected by gravity as the horizontal level of the switchbecame changed when the vehicle on which it was mounted ascended ordescended a grade.

The principal object of the present invention therefore is to eliminatethis objectionable feature by constructing the switch so that gravityeffect or action thereon is minimized, it can be arranged so that it mayassume a greater critical angle than the previous type before beingaffected by gravity, while at the same time the signal giving actionunder all conditions is positive and as sensitive as with the previoustype. The switch as now constructed also has the inherent feature ofabsorbing road shocks so that signals will not be unduly given when thevehicle is traversing rough roads.

A further object of the invention is to produce a simple and inexpensivedevice and yet one which will be exceedingly effective for the purposefor which it is designed.

These objects I accomplish by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claim.

In the drawing similar characters of reference indicate correspondingparts in the several views:

Figure /1 is a side elevation of the switch in a normal horizontal andinert position.

Figure 2 is a top plan view of the same.

Figure 3 is a sectional elevation of the switch when set on a slopeapproaching the predetermined critical angle.

Referring now more particularly to the characters of reference on thedrawing, the switch comprises a tube preferably of glass and of what maybe termed'acompound U-L or Y-L shape. In other words the horizontalportion of the switch 2 is substantially of U-shaped form and comprisesa pair of slightly diverging tube legs I both disposed in the samehorizontal plane and connected at one end by a neck 2. A tube leg 3 ofthe same diameter as the legs I projects upwardly at a forward anglefrom the front of the neck .centrally thereof so that said leg 3includes an obtuse angle with the plane of the legs I. In side elevationtherefore the tube is substantially L- shaped in form, while in plane itis Y-shaped in form, as clearly apparent from Figures 1 and 2respectively. Thetube as a whole is designed throughout witheasy curvesso as to reduce the resistance to mercury movement.

Toward the top the leg 3 is formed with a forwardly projectingsubstantially horizontal ledge 4; an electrode 5 projecting into the legfrom in front and below the ledge so as to terminate above the latteradjacent its forward end. Another electrode 6 projects downwardly intothe top of the leg 3 to a termination some distance above that of theelectrode 5. A third electrode 1 projects into the tube neck 2 from thebottom.

Mercury 8 in an amount suflicient to fill both legs land to extendupwardly into the leg 3 to a termination slightly above the level of theledge 4 is sealed in vacuum in the tube: The angle A included betweenthe horizontal legs I and a line L drawn through the top of the mercuryat both ends determining the critical angle at which the legs I may beset before the mercury will be acted on by gravity to cause said mercuryto rise in the leg 3. This angle is preferably chosen, and the switchdesigned accordingly, to correspond to a degee' of grade closelyapproaching what is ordinarily considered a dangerous grade.

When installing the switch in a motor vehicle, the legs I are of coursedisposed horizontal or parallel to the groundand if the switch is set sothat the leg 3 is at the forward end, the switch serves for slow andstopsignals particularly, as indicated in Figure 1. In such an installationthe electrode 5 is connected to the slow signal lights 9, the Ielectrode 6 is connected to the stop light Ill, while the electrode 1 isconnected to'a source of current. Signals may also be given uponreversing the car and if two switches are used set in reversed relationto each other, the following combination of signals can be given:

My improved switch is constructed to operate by the displacement ofmercury and on the well known law of physics that the mercury displacedin the leg 3 will equal the amount displaced from both horizontal legsI, which amount is of course double that displaced from eitherhorizontal leg individually. In other words, the mercury displaced fromboth horizontal legs will be combined in the leg 3 and the latter beingthe same diameter as the legs II, the extent of rise of mercury in theleg 3 will accordingly be twice the length of displacement of themercury in each individual leg l.

By reason of the position of the electrode 5 relative to the ledge d andthe position of the level of the mercury relative to the latter, contactof said electrode with the mercury is had with very slight displacementof the mercury in the legs ll,

so that the action is very sensitive as is desirable for the particularsignal connected to this electrode. It will therefore be seen that whatI term a multi-lift switch tube, which as far as I am aware employs anovel method of amplifying mercury displacement, overcomes the difiicultproblem of relative gravity directional changes on varying grades. Theprinciple of operation also, as previously stated, enables a relativelygreat critical angle to be used without interfering with the properoperation of the switch and also permits the electrodes to be spacedsuficiently far apart to avoid possible confusion in signal giving whileat the same time having the necessary positive and sensitive action.

The greater lifting potential or effect had in a tube of thisconstruction allows the greater tangential component lifting force inrounding curves, so that the switch will close a sectional surface theinstant a curve or side sway of any predetermined degree is encountered.Also this tube has the inherent feature of absorbing road shocks.

While I have here shown and describedand preferably used a switch tubehaving two horizontal legs, it will be obvious that the same principlemay be employed with the use of three or more legs, which would enablean even greater spacing between the electrodes in the upstanding legwhile maintaining the sensitiveness of operation.

From the foregoing description it will be readily seen that I haveproduced such a device as substantially fulfills the objects of theinvention as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of the device, stillin practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention, as defined by the appended claim.

Having thus described my invention what I claim as new and useful anddesire to secure by Letters Patent is:

A mercury inertia switch comprising a horizontal tube portion, anupstanding tube leg communicating with said horizontal portion at oneend thereof, mercury normally filling said portion and extending intothe upstanding leg a predetermined distance, a substantially horizontalledge formed on the interior of the upstanding leg adjacent the level ofthe top of the mercury therein and extending lengthwise of and away fromthe horizontal tube portion, and an electrode projecting into saidupstanding leg and terminating adjacent the outer end of said ledge.

REUBEN ERICH.

